
<html>
<head>
    <title>NeHe's OpenGL Lesson 18 for WebGl (Sphere)</title>
    <meta http-equiv="Content-Type" content="text/html; charset=utf-8">
    <style type="text/css">
        canvas {
            border: 2px solid black;
            -moz-box-shadow: black 2px 2px 2px;
            background-color: black;
        }
    </style>
    <script src="sylvester.js" type="text/javascript"></script>
    <script src="glUtils.js" type="text/javascript"></script>

    <!-- Fragment shader program -->

    <script id="shader-fs" type="x-shader/x-fragment">
        varying highp vec2 vTextureCoord;

        uniform sampler2D uSampler;

        void main(void) {
        gl_FragColor = texture2D(uSampler, vec2(vTextureCoord.s, vTextureCoord.t));
        }
    </script>

    <!-- Vertex shader program -->

    <script id="shader-vs" type="x-shader/x-vertex">
        attribute highp vec3 aVertexPosition;
        attribute highp vec2 aTextureCoord;

        uniform highp mat4 uNormalMatrix;
        uniform highp mat4 uMVMatrix;
        uniform highp mat4 uPMatrix;

        varying highp vec2 vTextureCoord;

        void main(void) {
        gl_Position = uPMatrix * uMVMatrix * vec4(aVertexPosition, 1.0);
        vTextureCoord = aTextureCoord;
        }
    </script>
</head>

<body>
<canvas id="glcanvas" width="640" height="480">
    Your browser doesn't appear to support the HTML5 <code>&lt;canvas&gt;</code> element.
</canvas>
<script type="text/javascript">
var canvas;
var gl;

var cubeVerticesBuffer;
var cubeVerticesTextureCoordBuffer;
var cubeVerticesIndexBuffer;
var cubeVerticesNormalBuffer;
var cubeRotation = 0.0;
var lastCubeUpdateTime = 0;

var cubeImage;
var cubeTexture;

var mvMatrix;
var shaderProgram;
var vertexPositionAttribute;
var vertexNormalAttribute;
var textureCoordAttribute;
var perspectiveMatrix;

var xrot=0.0,yrot=0.0,zrot=0.0;
var stacks = 64,slices = 128,radius=5;
var vertices = [];
var textureCoordinates = [];
var cubeVertexIndices = [];

start();
//
// start
//
// Called when the canvas is created to get the ball rolling.
//
function start() {
    canvas = document.getElementById("glcanvas");

    initWebGL();      // Initialize the GL context

    // Only continue if WebGL is available and working

    if (gl) {
        gl.clearColor(0.0, 0.0, 0.0, 1.0);  // Clear to black, fully opaque
        gl.clearDepth(1.0);                 // Clear everything
        gl.enable(gl.DEPTH_TEST);           // Enable depth testing
        gl.depthFunc(gl.LEQUAL);            // Near things obscure far things

        // Initialize the shaders; this is where all the lighting for the
        // vertices and so forth is established.

        initShaders();

        // Here's where we call the routine that builds all the objects
        // we'll be drawing.

        initBuffers();

        // Next, load and set up the textures we'll be using.

        initTextures();

        // Set up to draw the scene periodically.

        setInterval(drawScene, 15);

        document.addEventListener( 'keydown', onDocumentKeyDown, false );
    }
}

//
// initWebGL
//
// Initialize WebGL, returning the GL context or null if
// WebGL isn't available or could not be initialized.
//
function initWebGL() {
    gl = null;

    try {
        gl = canvas.getContext("experimental-webgl");
    }
    catch(e) {
    }

    // If we don't have a GL context, give up now

    if (!gl) {
        alert("Unable to initialize WebGL. Your browser may not support it.");
    }
}
//
// initBuffers
//
// Initialize the buffers we'll need. For this demo, we just have
// one object -- a simple two-dimensional cube.
//
function initBuffers() {
    var rho, drho, theta, dtheta;
    var x, y, z;
    var s, t, ds, dt;
    var i, j, imin=0, imax=0;
    var nsign = 1.0;

    drho = Math.PI / stacks;
    dtheta = 2.0 * Math.PI / slices;
    ds = 1.0 / slices;
    dt = 1.0 / stacks;
    t = 1.0; // because loop now runs from 0
    imax = stacks;

    // draw intermediate stacks as quad strips
    for (i = imin; i < imax; i++) {
        rho = i * drho;
        s = 0.0;
        for (j = 0; j <= slices; j++) {
            if(j == slices){
                console.log(1-s);
            }
            theta = (j == slices) ? 0.0 : j * dtheta;
            x = -Math.sin(theta) * Math.sin(rho);
            y = Math.cos(theta) * Math.sin(rho);
            z = nsign * Math.cos(rho);
            textureCoordinates[(i*(slices+1)+j)*4] = 1-s;
            textureCoordinates[(i*(slices+1)+j)*4+1] = t;
            vertices[(i*(slices+1)+j)*6] = x * radius;
            vertices[(i*(slices+1)+j)*6+1] = y * radius;
            vertices[(i*(slices+1)+j)*6+2] = z * radius;
            x = -Math.sin(theta) * Math.sin(rho + drho);
            y = Math.cos(theta) * Math.sin(rho + drho);
            z = nsign * Math.cos(rho + drho);
            textureCoordinates[(i*(slices+1)+j)*4+2] = 1-s;
            textureCoordinates[(i*(slices+1)+j)*4+3] = t - dt;
            s += ds;
            vertices[(i*(slices+1)+j)*6+3] = x * radius;
            vertices[(i*(slices+1)+j)*6+4] = y * radius;
            vertices[(i*(slices+1)+j)*6+5] = z * radius;

            if(j>0){
                cubeVertexIndices[(i*(slices+1)+(j-1))*6] = (i*(slices+1)+(j-1))*2;
                cubeVertexIndices[(i*(slices+1)+(j-1))*6+1] = (i*(slices+1)+(j-1))*2+1;
                cubeVertexIndices[(i*(slices+1)+(j-1))*6+2] = (i*(slices+1)+j)*2;
                cubeVertexIndices[(i*(slices+1)+(j-1))*6+3] = (i*(slices+1)+(j-1))*2+1;
                cubeVertexIndices[(i*(slices+1)+(j-1))*6+4] = (i*(slices+1)+j)*2;
                cubeVertexIndices[(i*(slices+1)+(j-1))*6+5] = (i*(slices+1)+j)*2+1;
            }
        }
        t -= dt;
    }

//    for(i = 0,j=0; j<vertices.length; i++,j=j+3){
//        cubeVertexIndices[i*3]   = i;
//        cubeVertexIndices[i*3+1] = i+1;
//        cubeVertexIndices[i*3+2] = i+2;
//        if((i+1)*3 == vertices.length){
//            cubeVertexIndices[i*3+1] = 0;
//            cubeVertexIndices[i*3+2] = 1;
//        }else if((i+2)*3 == vertices.length){
//            cubeVertexIndices[i*3+2] = 0;
//        }
//    }

    cubeVerticesBuffer = gl.createBuffer();
    gl.bindBuffer(gl.ARRAY_BUFFER, cubeVerticesBuffer);
    gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(vertices), gl.STATIC_DRAW);

    cubeVerticesTextureCoordBuffer = gl.createBuffer();
    gl.bindBuffer(gl.ARRAY_BUFFER, cubeVerticesTextureCoordBuffer);
    gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(textureCoordinates), gl.STATIC_DRAW);

    cubeVerticesIndexBuffer = gl.createBuffer();
    gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, cubeVerticesIndexBuffer);
    gl.bufferData(gl.ELEMENT_ARRAY_BUFFER, new Uint16Array(cubeVertexIndices), gl.STATIC_DRAW);
}

//
// initTextures
//
// Initialize the textures we'll be using, then initiate a load of
// the texture images. The handleTextureLoaded() callback will finish
// the job; it gets called each time a texture finishes loading.
//
function initTextures() {
    cubeTexture = gl.createTexture();
    cubeImage = new Image();
    cubeImage.crossOrigin = "";
    cubeImage.onload = function() { handleTextureLoaded(cubeImage, cubeTexture); }
    cubeImage.src = "textures/earth.jpg";
}

function handleTextureLoaded(image, texture) {
    gl.bindTexture(gl.TEXTURE_2D, texture);
    gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, gl.RGBA, gl.UNSIGNED_BYTE, image);
    gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.LINEAR);
    gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.LINEAR_MIPMAP_NEAREST);
    gl.generateMipmap(gl.TEXTURE_2D);
    gl.bindTexture(gl.TEXTURE_2D, null);
}

//
// drawScene
//
// Draw the scene.
//
function drawScene() {
    // Clear the canvas before we start drawing on it.

    gl.clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT);

    // Establish the perspective with which we want to view the
    // scene. Our field of view is 45 degrees, with a width/height
    // ratio of 640:480, and we only want to see objects between 0.1 units
    // and 100 units away from the camera.

    perspectiveMatrix = makePerspective(45, 640.0/480.0, 0.1, 100.0);

    loadIdentity();

    mvTranslate([0.0,0.0,-15.0]);

    mvRotate(yrot,[0.3,1.0,0.0]);
    mvRotate(90,[1.0,0.0,0.0]);
//    mvRotate(180,[0.0,0.0,1.0]);

    // Draw the cube by binding the array buffer to the cube's vertices
    // array, setting attributes, and pushing it to GL.

    gl.bindBuffer(gl.ARRAY_BUFFER, cubeVerticesBuffer);
    gl.vertexAttribPointer(vertexPositionAttribute, 3, gl.FLOAT, false, 0, 0);

    // Set the texture coordinates attribute for the vertices.

    gl.bindBuffer(gl.ARRAY_BUFFER, cubeVerticesTextureCoordBuffer);
    gl.vertexAttribPointer(textureCoordAttribute, 2, gl.FLOAT, false, 0, 0);

    // Specify the texture to map onto the faces.

    gl.activeTexture(gl.TEXTURE0);
    gl.bindTexture(gl.TEXTURE_2D, cubeTexture);
    gl.uniform1i(gl.getUniformLocation(shaderProgram, "uSampler"), 0);

    // Draw.
    gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, cubeVerticesIndexBuffer);
    setMatrixUniforms();
    gl.drawElements(gl.TRIANGLES, cubeVertexIndices.length, gl.UNSIGNED_SHORT, 0);

    xrot+=0.3;
    yrot+=0.2;
    zrot+=0.4;

    // Update the rotation for the next draw, if it's time to do so.

    var currentTime = (new Date).getTime();
    lastCubeUpdateTime = currentTime;
}

function onDocumentKeyDown ( event ) {
    //event.preventDefault();

}

//
// initShaders
//
// Initialize the shaders, so WebGL knows how to light our scene.
//
function initShaders() {
    var fragmentShader = getShader(gl, "shader-fs");
    var vertexShader = getShader(gl, "shader-vs");

    // Create the shader program

    shaderProgram = gl.createProgram();
    gl.attachShader(shaderProgram, vertexShader);
    gl.attachShader(shaderProgram, fragmentShader);
    gl.linkProgram(shaderProgram);

    // If creating the shader program failed, alert

    if (!gl.getProgramParameter(shaderProgram, gl.LINK_STATUS)) {
        alert("Unable to initialize the shader program.");
    }

    gl.useProgram(shaderProgram);

    vertexPositionAttribute = gl.getAttribLocation(shaderProgram, "aVertexPosition");
    gl.enableVertexAttribArray(vertexPositionAttribute);

    textureCoordAttribute = gl.getAttribLocation(shaderProgram, "aTextureCoord");
    gl.enableVertexAttribArray(textureCoordAttribute);
}

//
// getShader
//
// Loads a shader program by scouring the current document,
// looking for a script with the specified ID.
//
function getShader(gl, id) {
    var shaderScript = document.getElementById(id);

    // Didn't find an element with the specified ID; abort.

    if (!shaderScript) {
        return null;
    }

    // Walk through the source element's children, building the
    // shader source string.

    var theSource = "";
    var currentChild = shaderScript.firstChild;

    while(currentChild) {
        if (currentChild.nodeType == 3) {
            theSource += currentChild.textContent;
        }

        currentChild = currentChild.nextSibling;
    }

    // Now figure out what type of shader script we have,
    // based on its MIME type.

    var shader;

    if (shaderScript.type == "x-shader/x-fragment") {
        shader = gl.createShader(gl.FRAGMENT_SHADER);
    } else if (shaderScript.type == "x-shader/x-vertex") {
        shader = gl.createShader(gl.VERTEX_SHADER);
    } else {
        return null;  // Unknown shader type
    }

    // Send the source to the shader object

    gl.shaderSource(shader, theSource);

    // Compile the shader program

    gl.compileShader(shader);

    // See if it compiled successfully

    if (!gl.getShaderParameter(shader, gl.COMPILE_STATUS)) {
        alert("An error occurred compiling the shaders: " + gl.getShaderInfoLog(shader));
        return null;
    }

    return shader;
}

//
// Matrix utility functions
//

function loadIdentity() {
    mvMatrix = Matrix.I(4);
}

function multMatrix(m) {
    mvMatrix = mvMatrix.x(m);
}

function mvTranslate(v) {
    multMatrix(Matrix.Translation($V([v[0], v[1], v[2]])).ensure4x4());
}

function setMatrixUniforms() {
    var pUniform = gl.getUniformLocation(shaderProgram, "uPMatrix");
    gl.uniformMatrix4fv(pUniform, false, new Float32Array(perspectiveMatrix.flatten()));

    var mvUniform = gl.getUniformLocation(shaderProgram, "uMVMatrix");
    gl.uniformMatrix4fv(mvUniform, false, new Float32Array(mvMatrix.flatten()));

    var normalMatrix = mvMatrix.inverse();
    normalMatrix = normalMatrix.transpose();
    var nUniform = gl.getUniformLocation(shaderProgram, "uNormalMatrix");
    gl.uniformMatrix4fv(nUniform, false, new Float32Array(normalMatrix.flatten()));
}

var mvMatrixStack = [];

function mvPushMatrix(m) {
    if (m) {
        mvMatrixStack.push(m.dup());
        mvMatrix = m.dup();
    } else {
        mvMatrixStack.push(mvMatrix.dup());
    }
}

function mvPopMatrix() {
    if (!mvMatrixStack.length) {
        throw("Can't pop from an empty matrix stack.");
    }

    mvMatrix = mvMatrixStack.pop();
    return mvMatrix;
}

function mvRotate(angle, v) {
    var inRadians = angle * Math.PI / 180.0;

    var m = Matrix.Rotation(inRadians, $V([v[0], v[1], v[2]])).ensure4x4();
    multMatrix(m);
}
</script>
</body>
</html>